install-string-output-character-strategy

Arguments:
stream

This function is called for its side-effects. Its return value is
unspecified. This function installs output character handlers into the
stream that are appropriate for string-streams,
and also sets the external-format state slots to nil.

You must load the :iodefs module to use this
function. Do that by evaluating (require :iodefs). (It
is not an error to evaluate that form if the module is already
loaded.) This function is intended for implementing device-level
functionality and should not be used except for that purpose. See Simple-stream Description
in streams.htm for a description of the device-level.